Wyred 4 Sound ST-750LE Stereo Power Amplifier

Wyred 4 Sound ST-750LE Stereo Power Amplifier

The new Wyred 4 Sound ST-750LE stereo power amplifier sounds far above it's price class. The technology includes Wyred 4 Sound's proprietary input circuit that is similar to the one implemented in their '10 LP'-rated STP-SE Stage 2 preamplifier. This is followed by the latest IcePower amplifier module. The base price of the amplifier is $1599.00. The review sample is also equipped with the WBT speaker binding posts and Kimber TCX wire upgrade, a $250 option.

From the Wyred 4 Sound Web site:
"For the ST-750, we decided to use the new 700AS2 module from ICEpower. Originally thinking this followed the same design platform as the 1200AS module, we thought it would be good to inject some newer circuitry to our lineup. Although it is not made with the new ICEedge topology, this module is the newest non-ICEedge circuit and was the logical stepping stone for ICEpower to use before completing the ICEedge standard found in the 1200AS1/2 module.

"The 700AS2 module is a stereo full bridge design. We usually have a concern when not using a dual mono design (found in other stereo amps in our line) but the isolation and pure robustness of this amp should not be understated. It offers the most generous continuous output power without thermal shutdown and a powersupply to far exceed that. Channel separation meets or exceeds our other multi-mono designs as well."

Other components on hand during the audition include a VPI Aries 3 turntable with a Kuzma 4-Point tonearm; ZYX UNIverse Premium, ZYX Optimum, and Miyajima Madake moving coil cartridges; B.M.C. MCCI ULN phono preamplifiercustom Windows 10 music computer running JRiver Media Center; Wyred 4 Sound DAC 2v2SE 10th Anniversary DA converter; RME ADI-2 Pro AD/DA converter with external power supply; Pass Labs XP-22, BAT VK-43SE, and Wyred 4 Sound STP-SE Stage 2 preamplifiers; Valvet E2, Primaluna Prologue 5 and Prologue Premium, Ayre VX-5, and Conrad-Johnson Classic 62SE power amplifiers; Focal Sopra 1 loudspeakers with the lowest few Hertz supplied by a pair of JL Audio e110 subwoofers, Revel Performa BE M126Be, Monitor Audio PL100 II, and Focal Chorus 714 loudspeakers borrowed from the HT system. The audio cabling is Audioquest WEL Signature and Mogami interconnects and speaker cables. USB cables are Straight Wire USB-F. Power cords include my DIY power cord and Straight Wire Pro Thunder. Power protection and purification are provided by a PS Audio Dectet for the preamplifiers and source components, and a PS Audio Quintet for the power amplifiers. The Quintet includes a standard 1/8" trigger for remote turn-on and -off of power amplifiers that lack a 12V remote trigger.

The ST-750LE offers both RCA and XLR inputs, a trigger input and output, and the expected light weight of Class D amplifiers: about 13 pounds. A 5-year warranty for the original purchaser is included. The rated power output is 350 Watts per channel. My audition never approached that power level and the amplifier always operated just above ambient temperature. Break in is a necessity, with 100 hours as the recommended minimum. The amplifier is well done at about 300-500 hours, depending on how loudly the break in is performed. The following response was heard several times during the break in interval: “But honey, I’m breaking in a new amplifier. It NEEDS to be loud!” Good luck with that one. 

I break in amplifiers with a tuner as the signal source, a breadboard with RCA jacks and a stereo 50k Ohm potentiometer for attenuation, and 10 Watt 8 Ohm resistors instead of speakers. After 150 hours of that, the first listen was not at all unpleasant and turned into a late evening of thoroughly enjoying the music. Typically, a new component will start to showcase its unique character, AKA flaws, after an hour or two, but the Wyred 4 Sound amplifier provided very enjoyable listening experiences for days and weeks and its character was understood.

The ST-750LE delivers outstanding dynamic power, both large-scale macro and small-scale micro dynamics. This character imbues the music with propulsion and energy, carrying the listener along for an exciting ride. It also sings sweetly, delivering quieter music with intimacy and warmth. Everything from explosions to tiny taps of a drumstick are delivered with excellent clarity. Listen to “Mountain Jam” from the Allman Brothers Band’s Eat a Peach LP. The drum jam starting around the 12-minute mark is very powerful and entertaining. The snare drum, and the very obvious clarity of the toms and bass drum are all wonderful to hear. We can clearly hear the beater of the bass drum pedal hitting the drum head. This is a great example that not only is the bass resolution very good, but also is the leading edge of the attack or impulse. The amplifier’s instantaneous delivery of impulsive, dynamic changes is thoroughly correct and true to the recording.

The bass is very extended and will test the bass range of any loudspeaker. The Ayre VX-5 has a leaner, tighter character in the lowest octave (the amplifier’s best quality), while the ST-750LE offers satisfying bass. Above about 100 Hz, the Wyred 4 Sound amp surpasses the Ayre and gives the other amps on hand some good competition.

Listening to “Tom’s Diner” by Suzanne Vega, from the KBCO Studio C, Volume 20 CD, resulted in spontaneous laughter because Suzanne sounded so human, so accessible, so present. On the same CD, "Shakedown Street" performed by Phil Lesh & Friends is jamming. If you're not diggin' it, you're dead. Released one year later, the KBCO Studio C, Volume 21 CD, Michael Franti’s “Say Hey (I Love You)” is terrifically focused and open, with no sign of congestion. The musicians on a large sound stage remain separate and distinct at any safe volume level, which means infrequent 100 dB peak SPL. 

The strong bass line in Steely Dan’s “Black Crow”, on the Aja LP from Mobile Fidelity Sound Labs, sounds very linear into the lowest bass notes with excellent power and detail. The cymbals at about the 3-minute mark are rendered with outstanding tone and fine detail.

The soundstange is large. "Danse Macabre, Op. 40" on Witches Brew, RCA Victor Living Stereo LP, LSC-2225 Red Seal, presents a stage that extends outside of the speakers, and nicely deep to highlight the percussion at the rear of the stage when called for. The placement of the rows of strings and the brass section is unambiguous.

On “Samsonite Man” on the Alicia Keys LP The Diary of Alicia Keys, the background vocals, including dubs of Alicia herself, are spread across the space between the speakers with very good depth of tone. The bells at the beginning and at the end of the song are sweetly presented at the edge of hearing.

Compared to the Conrad-Johnson Classic 62SE, the C-J delivers a bit more fine detail, exactly what keeps tube lovers enamored with the older technology. Some of this detail, however, is not a question of quality, but can be attributed to voicing and other non-linearities. The C-J stage is deeper, which includes more fully formed performers. The bass character of the C-J amp is quite similar to the ST-750LE, although the Wyred 4 Sound amplifier is stronger, more under control in the lowest bass. The Wyred 4 Sound amp has much better treble purity than the C-J and Primaluna vacuum tube amps. The ST-750LE has a purity and ease that is closer to the sought-after single-ended sound. The overall character is similar to my memory of the PS Audio Stellar S300, which was not available for direct comparison.

The Primaluna Prologue Premium, a late version that is identical to the brand new EVO 200, has the most prominant treble range of this field of amplifiers. The Primaluna has EL34 power tubes. Relative to the other amplifiers, it is more "forward" and seemingly louder in the mid and upper treble. In order of this relative character, with the Primaluna amps being the most treble-apparent, next is the Valvet E2, followed by the Wyred 4 Sound ST-750LE, with the C-J Classic 62SE being the least treble-forward, most laid back of this group. The Classic 62SE has KT-120 power tubes. This example contradicts the common ideas about the character of EL34 vs. KT-120. 

Each one of us values specific aspects of music reproduction. Some of you listen for a well developed sound stage, or maybe a beautiful and correct midrange is paramount. This listener is particularly interested in the special character of the single-ended sound. No other technology seems able to deliver music as correctly as single-ended amplification does. For example, push-pull amps - both tube and solid state - often sound somewhat distorted in the treble, as if the waveforms of the “push” and “pull” are not assembled perfectly by the amplifier. In this regard, one that is a make-or-break character, the ST-750LE easily beats all of the amplifiers above except for the single-ended Valvet E2. This elevates the long-term listening enjoyment of the ST-750LE above these more-expensive amplifiers. If you share this feeling that something is not quite right with the sound of most amplifiers, the vast majority of which are push-pull, then check out the ST-750LE. It does not have the very slight, almost subliminal coarseness of the Hypex amps in my experience, which includes UcD, and Ncore 400, 500, and 1200.

The Wyred 4 Sound amplifier provides excellent sound with all of the preamplifiers, whether with the tube-like BAT VK-43SE or the more linear sounding Wyred 4 Sound STP-SE Stage 2 preamp. Not surprisingly, the Wyred 4 Sound STP-SE Stage 2, my long-term reference due to its unmatched freedom from any character, works very well with the company’s amplifier. 

This amplifier does nothing wrong. It has a unique character which is a cross between tube and solid-state sound, largely made up of a couple of small – and possibly system dependent – recesses. You can buy more detail in the bass and upper treble. But what this amplifier delivers is consistent listening enjoyment and involvement. Long, tireless listening sessions are standard. The RCA inputs have a very slight benefit in that upper-treble area, while the XLRs benefit the bass and midrange. This last observation is probably system dependent, relating to the 5-meter interconnects in use between the preamplifier and power amplifier.

If we rank-order the amplifiers on hand for relatively the most entertaining and enjoyable amplifier to the least, the entirely subjective order is:
Valvet E2
Wyred 4 Sound ST-750LE
Primaluna Prologue Premium
C-J Classic 62SE
Primaluna Prologue 5
Ayre VX-5

This latest model from the keen minds at Wyred 4 Sound bridges the gap between the purity of single-ended amplifiers and the power and dynamics of good push-pull amplifiers, tube or solid state. The ST-750LE delivers very enjoyable, long-term listening because it adds nothing objectionable to your music. While it is not the top choice in the list above, that amplifier delivers only 12 Watts per channel which obviously limits its compatibility with many speakers. For this reviewer’s equipment needs, the Wyred 4 Sound ST-750LE offers an excellent sounding, powerful, cool-running power amplifier that has become a reliable reference.

Overall Rating: 9.5 LPs

This review would not have been possible without the kind and generous support of EJ Sarmento of Wyred 4 Sound. Thank you, EJ!

Link to manufacturer: Wyred 4 Sound